/* eslint-env amd */
define([
	'./code-path-state',
	'./id-generator'
],
function(CodePathState, IdGenerator) {
	/**
	 * @fileoverview A class of the code path.
	 * @author Toru Nagashima
	 */

	"use strict";
	//------------------------------------------------------------------------------
	// Public Interface
	//------------------------------------------------------------------------------

	/**
	 * A code path.
	 *
	 * @constructor
	 * @param {string} id - An identifier.
	 * @param {CodePath|null} upper - The code path of the upper function scope.
	 * @param {function} onLooped - A callback function to notify looping.
	 */
	function CodePath(id, upper, onLooped) {

		/**
		 * The identifier of this code path.
		 * Rules use it to store additional information of each rule.
		 * @type {string}
		 */
		this.id = id;

		/**
		 * The code path of the upper function scope.
		 * @type {CodePath|null}
		 */
		this.upper = upper;

		/**
		 * The code paths of nested function scopes.
		 * @type {CodePath[]}
		 */
		this.childCodePaths = [];

		// Initializes internal state.
		Object.defineProperty(
			this,
			"internal", {
				value: new CodePathState(new IdGenerator(id + "_"), onLooped)
			});

		// Adds this into `childCodePaths` of `upper`.
		if (upper) {
			upper.childCodePaths.push(this);
		}
	}

	CodePath.prototype = {
		constructor: CodePath,

		/**
		 * The initial code path segment.
		 * @type {CodePathSegment}
		 */
		get initialSegment() {
			return this.internal.initialSegment;
		},

		/**
		 * Final code path segments.
		 * This array is a mix of `returnedSegments` and `thrownSegments`.
		 * @type {CodePathSegment[]}
		 */
		get finalSegments() {
			return this.internal.finalSegments;
		},

		/**
		 * Final code path segments which is with `return` statements.
		 * This array contains the last path segment if it's reachable.
		 * Since the reachable last path returns ``.
		 * @type {CodePathSegment[]}
		 */
		get returnedSegments() {
			return this.internal.returnedForkContext;
		},

		/**
		 * Final code path segments which is with `throw` statements.
		 * @type {CodePathSegment[]}
		 */
		get thrownSegments() {
			return this.internal.thrownForkContext;
		},

		/**
		 * Current code path segments.
		 * @type {CodePathSegment[]}
		 */
		get currentSegments() {
			return this.internal.currentSegments;
		},

		/**
		 * Traverses all segments in this code path.
		 *
		 *     codePath.traverseSegments(function(segment, controller) {
		 *         // do something.
		 *     });
		 *
		 * This method enumerates segments in order from the head.
		 *
		 * The `controller` object has two methods.
		 *
		 * - `controller.skip()` - Skip the following segments in this branch.
		 * - `controller.break()` - Skip all following segments.
		 *
		 * @param {object} [options] - Omittable.
		 * @param {CodePathSegment} [options.first] - The first segment to traverse.
		 * @param {CodePathSegment} [options.last] - The last segment to traverse.
		 * @param {function} callback - A callback function.
		 * @returns {void}
		 */
		traverseSegments: function(options, callback) {
			if (typeof options === "function") {
				callback = options;
				options = null;
			}

			options = options || {};
			var startSegment = options.first || this.internal.initialSegment;
			var lastSegment = options.last;

			var item = null;
			var index = 0;
			var end = 0;
			var segment = null;
			var visited = Object.create(null);
			var stack = [
				[startSegment, 0]
			];
			var skippedSegment = null;
			var broken = false;
			var controller = {
				skip: function() {
					if (stack.length <= 1) {
						broken = true;
					} else {
						skippedSegment = stack[stack.length - 2][0];
					}
				},
				break: function() {
					broken = true;
				}
			};

			/**
			 * Checks a given previous segment has been visited.
			 * @param {CodePathSegment} prevSegment - A previous segment to check.
			 * @returns {boolean} `true` if the segment has been visited.
			 */
			function isVisited(prevSegment) {
				return visited[prevSegment.id] ||
					segment.isLoopedPrevSegment(prevSegment);
			}

			while (stack.length > 0) {
				item = stack[stack.length - 1];
				segment = item[0];
				index = item[1];

				if (index === 0) {

					// Skip if this segment has been visited already.
					if (visited[segment.id]) {
						stack.pop();
						continue;
					}

					// Skip if all previous segments have not been visited.
					if (segment !== startSegment &&
						segment.prevSegments.length > 0 &&
						!segment.prevSegments.every(isVisited)
					) {
						stack.pop();
						continue;
					}

					// Reset the flag of skipping if all branches have been skipped.
					if (skippedSegment && segment.prevSegments.indexOf(skippedSegment) !== -1) {
						skippedSegment = null;
					}
					visited[segment.id] = true;

					// Call the callback when the first time.
					if (!skippedSegment) {
						callback.call(this, segment, controller); // eslint-disable-line callback-return
						if (segment === lastSegment) {
							controller.skip();
						}
						if (broken) {
							break;
						}
					}
				}

				// Update the stack.
				end = segment.nextSegments.length - 1;
				if (index < end) {
					item[1] += 1;
					stack.push([segment.nextSegments[index], 0]);
				} else if (index === end) {
					item[0] = segment.nextSegments[index];
					item[1] = 0;
				} else {
					stack.pop();
				}
			}
		}
	};

	/**
	 * Gets the state of a given code path.
	 *
	 * @param {CodePath} codePath - A code path to get.
	 * @returns {CodePathState} The state of the code path.
	 */
	CodePath.getState = function getState(codePath) {
		return codePath.internal;
	};

	return CodePath;
});